Transcript Vegetative Reproduction in Plants

Asexual Reproduction
in Plants
Vegetative Propagation
Contents
Definition
Modified Stems
Modified Roots
Modified Leaves
Modified Buds
Sexual Vs Asexual
Reproduction
Vegetative Propagation
Cuttings
Grafting
Layering
Budding
Micropropagation
(Tissue Culture)
Cloning
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Definition
asexual reproduction: does not involve the
manufacture or union of sex cells or gametes
e.g. binary fission, fragmentation, spore formation
and budding
- involves only one parent and offspring are
genetically identical (have the same genetic
content) to parent.
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What happens?
Part of the plant becomes separated from the parent
plant and grows into a new plant.
New plants generally develop from an axillary bud
of the parent plant.
Parts of the parent plant are specially modified for
the purpose.
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Modified Stems
Runners: horizontal running over the soil surface terminal bud of the runner sends up new shoots
e.g. strawberry, creeping buttercup.
Stem Tubers: swollen underground stem tip - buds
(eyes) produce new shoots e.g. potato
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Runners e.g. strawberries
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Stem tubers e.g. potatoes
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Modified Roots
Root Tuber: swollen fibrous roots — no eyes (buds)
e.g. dahlia, lesser celandine
Note:
Tap Root: swollen roots for food storage - not a
reproductive organ - biennial plants e.g. carrot,
turnip
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Root tuber e.g. dahlia
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Modified Leaves
Some plants produce plantlets along the edges of the
leaves.
Plantlets reach a certain size, fall off and grow into
new plants e.g. Bryophyllum (mother of thousands)
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Bryophyllum with plantlets
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Modified Buds
Bulbs: swollen underground bud with fleshy leaves
and reduced stem e.g. daffodil, onion, tulip
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An onion bulb
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Bulb – swollen leaves on a flat stem
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Sexual (Seed) Vs Asexual
(Vegetative) Reproduction
(1/2)
Cross pollination ensures
variation
More resistant to disease.
Dispersal reduces
competition.
Seeds can remain dormant
and survive unfavourable
conditions
Sexual reproduction favours
evolution
Sure of establishing new
daughter plant
New plants well developed
before separating from
parent
Retain parental genotype.
New plants obtained in a
shorter time.
Only one parent needed.15
Sexual Vs Asexual Reproduction
Seed production - complex.
A lot of seed produced - few
new plants obtained.
Pollination + dispersal
depend on external agents.
Seeds + fruits eaten by
animals
(2/2)
Grow in clumps competition for minerals,
light, space.
Susceptible to disease - all
genetically similar - clones
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Vegetative propagation
vegetative propagation: reproduction not involving
seed
Two types:
Natural e.g. rhizomes, corms, tubers, bulbs,
Artificial - used by gardeners to propagate plants
e.g. cuttings, layering, grafting, and budding.
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Cuttings
cutting: slip removed from plant and rooted in water
or well-watered compost e.g. busy lizzie,
geranium.
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Grafting
grafting: method of plant propagation where the
scion (i.e. the plant to be propagated) is attached to
the stock (i.e. the plant onto which it is grafted)
e.g. apple trees.
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Layering
layering: method of artificial / vegetative
propagation where a branch of a plant is bent over
and pinned to the earth at a node.
When roots develop the branch is separated from the
parent plant.
Useful for the propagation of woody plants e.g.
blackberry, gooseberry.
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Budding
budding: a method of plant propagation where a bud
(of a rose) is attached to the stock (of a briar) e.g.
roses.
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Micropropagation (Tissue Culture)
(1/2)
Cells removed from a plant or animal and grown as a
tissue culture in a special culture medium.
An entire plant can be grown from a small piece of
stem, leaf or root tissue.
Once the tissue develops into a plantlet it can be
divided up again to produce many identical plants.
Used in mass production of house plants and crops
such as bananas, strawberries and oil palm trees.
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Micropropagation (Tissue Culture)
(2/2)
Provides a larger number of plants more quickly than
cuttings.
Can be used to check cells for a particular feature
e.g. resistance to chemicals or a particular disease.
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Tissue culture in the laboratory
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Micropropagation of oil palm trees
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Cloning
clone: all offspring genetically identical - produced
asexually i.e. all have come from one original
parent e.g. King Edward potato.
Clones are produced by mitosis.
All the offspring from the various methods of
vegetative reproduction (both natural and artificial)
mentioned above are examples of clones.
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END
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